If we choose to live near convergent plate boundaries, we can build buildings that can resist earthquakes, and we can evacuate areas around volcanoes when they threaten to erupt. Yes, convergent boundaries are dangerous places to live, but with preparation and watchfulness, the danger can be lessened somewhat.
Nitrification, as stated above, is formally a two-step process; in the first step ammonia is oxidized to nitrite, and in the second step nitrite is oxidized to nitrate. Different microbes are responsible for each step in the marine environment.
The nitratation is the second part of the nitrification. The NOB uses the enzyme nitrite oxidoreductase (NOR) to conduct the process. The reaction is happening in two steps (here step 4 and step 5). Step 4: NH 3 NO 2 - is oxidized into NO 3 - with the help of the NOR enzyme.